In the operative treatment of fractures of the femur, combination fractures of the femur neck and shaft cause the greatest problems, because of the incompatible osteosynthetic procedures for these two different types of fractures.
In the current state of the art, femur shaft fractures are immobilized with intramedullar nails or pins. Femur-neck fractures are immobilized with angular plates, hip screws, or by means of three screws inserted in parallel. In younger patients the screw method is the principal method used, because this type of treatment causes the least additional damage to the femur neck.
As regards the urgency with which the two fractures must be immobilized, treating the femur neck fracture is the most immediate. With this type of fracture there is a danger that if it is not immobilized, a circulatory disturbance will occur in the femur head. Most such circulatory disturbances end in a resection of the femur head and the installation of a full prosthesis. In contrast to this complication, a delay in treating a fracture in the femur shaft is easier to deal with. Nevertheless, use of intramedullary implants for immobilizing this type of combination fracture is becoming increasingly frequent. Such intramedullary nails or pins have at their proximal end cross-holes for screws to be inserted laterally through the intramedullary pin into the femur head.
The screws needed for immobilizing the femur-neck fracture have a diameter of at least 6.5 mm., and are inserted in parallel fashion into the femur head. Because of the intramedullary pin, these screws can be inserted only one below the other, and so only two screws can be inserted through the pin into the femur head.
To ensure that the intramedullary pin is not too greatly weakened by the two cross-holes and the additional conveying of force via the screws, the intramedullary pin is made larger in diameter than would otherwise be used. This larger diameter requires a larger drilling of the medulla, which is out of proportion to the shaft fracture to be immobilized.
However, the principal disadvantage of this osteosynthetic procedure is that the shaft fracture is treated first, before the femur-neck fracture can be stabilized. The disadvantage of this method becomes particularly apparent when we realize the amount of force needed to drive in an intramedullary pin. Every blow needed to drive in the pin further separates the fracture in the neck area, which inevitably threatens the blood supply in the femur head area.